In fossil-fired power plants for generation of electrical power, the combustion of a fossil fuel gives rise to a carbon dioxide-containing flue gas. To avoid or to reduce carbon dioxide emissions, carbon dioxide has to be removed from the flue gases. In general, various methods are known for removal of carbon dioxide from a gas mixture. Especially for removal of carbon dioxide from a flue gas after a combustion operation, the method of absorption-desorption is commonly used. On the industrial scale, carbon dioxide (CO2) is scrubbed out of the flue gas in an absorber with an absorption liquid (CO2 capture operation).
Commonly used absorption liquids (solvents) are based on primary, secondary or tertiary amines and exhibit good selectivity and high capacity for carbon dioxide CO2.
The advantage of secondary amine compounds (secondary amines or secondary amino acid salts) over primary amine compounds (primary amines or primary amino acid salts) lies in the much lower absorption energy and the resulting lower regeneration energy, which is perceptible in a smaller drop in efficiency of the power plant. Furthermore, secondary amine compounds exhibit a higher loading capacity for CO2. One advantage of the primary amine compounds is the much faster absorption kinetics. This allows the columns of a CO2 capture plant to be designed smaller compared to the secondary amines or secondary amino acid salts, which leads to lower capital costs.
The advantage of amino acid salts compared to heterocyclic amines or alkanolamines is that amino acid salts do not have any noticeable vapor pressure, and thus do not evaporate and cannot be discharged into the environment by the CO2 capture operation. Heterocyclic amines and alkanolamines are volatile and are also discharged by the flue gas emitted into the environment, which leads to unwanted environmental pollution.
In the chemical industry, principally the primary amine MEA (monoethanolamine) is being used at the present time. Since the energy efficiency is not at the center of interest in the chemical industry, the energetic disadvantages have been very substantially neglected to date. In power plants, in contrast, it is precisely the energy consumption of the CO2 capture operation which is of great significance, since it has a considerable influence on the overall efficiency of the power plant due to its size. This industrial conversion is currently the subject of research and development, which is why this problem is currently being optimized to a high degree.